An audio receiver component is a source of audio output for computing devices, such as with mobile devices that are used for telephony. With mobile computing devices, numerous enhancements have been made to the manner in which the audio receiver component is housed within a mobile device. Prior approaches to housing an audio receiver component have had to balance structural considerations with the need to efficiently produce quality audio. Some past approaches have provided for sealing the volume to the rear of the audio receiver component (“rear volume”). Still, other approaches have incorporated air leaks into the rear volumes, while other approaches have relied on a multiple port structure in the rear volume to introduce resonant effects at specific ranges in the audible bandwidth. Each of these conventional approaches have drawbacks.
For example, a majority of mobile devices use a sealed rear volume, positioned opposite to the direction that sound is output from the receiver component. The sealed rear volume enables the receiver component to output audio, but severely limits the pre-filtered bandwidth of the system at low frequencies (<500 Hz). This creates the need for aggressive digital signal processing (DSP) filtering to bring the system's frequency response within passing range of mandated tolerance masks. The need for DSP filtering is an added cost, and consumes battery and software resources.
Other audio receiver component designs implement a so-called leaky rear volume. There are many problems with an uncontrolled/leaky rear volume. First, if the receiver rear volume has an uncontrolled leak into the housing of the device, the device becomes much more susceptible to echo because an internal path is created between the device's receiver and its microphone. Although the internal leak may help gain back some bandwidth at low frequencies, there may be other parasitic resonance effects created.
Still further, another approach has been to include multiple port structures into the receiver rear volume. However, in a device with a ‘candy bar’ configuration, the additional ports are generally located next to the main receiver port (adjacent to the user's ear). Such an approach unnecessarily reduces the efficiency of the receiver system.